1. Field of the Invention
The present invention relates to a permanent magnet excited transverse flux linear motor and, more particularly, to a permanent magnet excited transverse flux linear motor with a normal force compensation structure in which a stator is inserted in the middle of leg portions of a mover so as to compensate normal forces generated between the mover and the stator, thus reducing noise and vibration.
2. Description of Related Art
In general, a motor is a device that converts electrical energy into mechanical energy and fundamentally requires a high output power (output power/motor weight: kW/kg) and a high efficiency (output power/input power).
Especially, in a case where linear motion is obtained using a power transmission system such as a rotary motor, a ball screw, etc., the system becomes complicated and produces particles and dusts, thus it cannot form a clean transfer system. Accordingly, the use of linear motors has been increased recently in linear transmission systems.
The linear motors may be classified into a longitudinal flux motor and a transverse flux motor according to the direction of a magnetic flux.
Here, the direction of the magnetic flux is the same as the moving direction of the motor in the longitudinal flux motor, whereas, the direction of the magnetic flux is transverse to the moving direction of the motor in the transverse flux motor.
That is, in case of the longitudinal flux motor, the direction of an applied current is perpendicular to the moving direction of the motor, whereas, in case of the transverse flux motor, the direction of an applied current is the same as the moving direction of the motor.
In the transverse flux motor, a space (electrical circuit) in which a winding can be performed is separated from a space (magnetic circuit) in which a magnetic flux can flow. Accordingly, the transverse flux motor can increase the output power density and provide a variety of designs, compared with the longitudinal flux motor in which the electrical circuit and the magnetic circuit are coupled with each other.
Moreover, the transverse flux motor has advantages in that the copper loss is small and the amount of copper used therein is small, since the winding is provided in the form of a ring, compared with the longitudinal flux motor having a lot of end-windings.
Meanwhile, as well known in the art, since a linear motor is large in volume and uses many permanent magnets, the size of the system is large and its price is high.
To solve such problems, it is possible to use permanent magnet excited transverse flux linear motors that generate a high thrust force per unit weight and require a smaller number of expensive permanent magnets.
However, it has been known that the existing permanent magnet excited transverse flux linear motors have numerous limitations in their use due to noise and vibration caused by the normal forces and the pulsation of the thrust force.
Especially, since the permanent magnet excited transverse flux linear motor has a structure in which the mover faces the stator and the left and right normal forces are applied to the mover and stator structure, large normal forces are generated to cause noise and vibration.
Accordingly, it is necessary to provide an improved method of reducing the noise and vibration by compensating the normal forces in the permanent magnet excited transverse flux linear motor.
Moreover, since the magnetic flux of the existing permanent magnet excited transverse flux linear motor flows three dimensionally, an ordinary laminated iron core cannot be used, therefore a solid iron core is used. However, in a case where the solid iron core is employed, the motor performance deteriorates, and the deterioration becomes severe due to iron loss in a high speed range.